The embodiments described herein relate to methods and processes for recycling base oils from spent invert emulsion drilling fluids.
Drilling fluids are circulated through a wellbore during a drilling operation, for example, to remove cuttings (i.e., small pieces of the formation that break away during drilling) and to cool the drill bit. In some instances, drilling fluids are an oil-based fluid that includes a weighting agent. Typically, weighting agents include particles of high-density minerals that increase the density of the drilling fluid. Increasing the density of the drilling fluid may help to stabilize the wellbore and mitigate formation fluid intrusion into the wellbore.
As drilling fluids are circulated through the wellbore during the drilling process, the drilling fluids collect drilled solids or “cuttings.” These cuttings affect the properties of the drilling fluid. Accordingly, drilling fluids may be passed through a series of processes or apparatuses to remove the cuttings (e.g., vibrating screens for filtration). However, as the drilling continues, the cuttings are further broken down into smaller and smaller particles that cannot be effectively removed by normal mechanical means. Further, the density of cuttings is often sufficiently low that gravity or centrifugal methods to remove the cuttings is inefficient or ineffective. Once the properties of the drilling fluid are deemed unfit for drilling, the drilling fluid is considered to be a “spent” drilling fluid that is now waste.
Disposing of spent drilling fluid may involve burning the contents in a cement kiln. Some have attempted to recover the oil from the drilling fluid. For example, the spent drilling fluid may be heated in a high temperature calciner to vaporize the fluid that can then be condensed and recovered. However, high temperature processes can be energy intensive and, in some instances, may crack or degrade the oil, which reduces the ability to reuse the oil in a new drilling fluid.